It's not entirely my story to tell so I'll keep it vague.
It turned out a guy I considered my family groomed someone he met through me. His victim recently confided in me what he did to her years ago. I believed her so I confronted aforementioned "best friend" who spent more energy trying to gain sympathy over how he was "in a dark place" and that's why he did what he did than acknowledging that he did something absolutely despicable. I kicked him out of my place and told him he's dead to me. I'm still in the fallout of the whole situation.